1. Field of the Invention
This invention relates to sewing machine frames which include one or more removable covers, and more particularly, to a novel frame and cover construction and fastening means for securing the cover to the frame without disturbing the dimensional stability of the sewing machine frame.
2. Description of the Prior Art
U.S. Pat. Nos. 2,678,011, May 11, 1954, Peets et al and 3,467,041, Sept. 16, 1969, Greulich, typify the prior art approach to sewing machine frame cover construction and fastening. In the prior art approach contiguous surfaces usually planer mating surfaces, are formed on the frame and on the cover and fasteners are provided designed to draw and maintain all of the mating surfaces into engagement with each other. Because sewing machine frames and covers were fabricated heretofor primarily of metal without severe warpage characteristics and because machining steps to correct any slight dimensional variations were acceptable in the prior art, this typical mode of frame and cover construction and fastening was acceptable and provided uniformly spaced joints between the parts.
With the advent of modern day synthetic materials for sewing machine frames and covers, the susceptibility of warpage, particularly of covers, has increased and competitive pressures have militated against use of costly additional machining steps in frame and cover manufacture to correct for such warpage of parts. As a result, a warped cover, if shaped and fastened as in the prior art, would be distorted by tightening of the fastening means and consequently, would impart undesirable stresses to the sewing machine frame which can cause misalignment of the stitch forming instrumentalities and contribute to faulty or inoperative stitch formation.